There is Redmi 7 (12.5.3.0 xiaomi.eu Android 10)
In the system of the MTS operator (Russia), it is perfectly registered in IMS, and all Voice over LTE (VoLTE) and Wi-Fi Calling (VoWiFi /VoWLAN) services work
In the operator's system, Megafon (Russia) registers with IMS, but only Voice over LTE (VoLTE) works, the Wi-Fi Calling service (VoWiFi/VoWLAN) does not work.
Considering the work of the operator to promote IMS services, the support and correct operation of the IMS module is vital!
It may be worth updating the IMS operator profiles every six months and releasing updated firmware versions, or offering an update module.
In the system of the MTS operator (Russia), it is perfectly registered in IMS, and all Voice over LTE (VoLTE) and Wi-Fi Calling (VoWiFi /VoWLAN) services work
In the operator's system, Megafon (Russia) registers with IMS, but only Voice over LTE (VoLTE) works, the Wi-Fi Calling service (VoWiFi/VoWLAN) does not work.
Considering the work of the operator to promote IMS services, the support and correct operation of the IMS module is vital!
It may be worth updating the IMS operator profiles every six months and releasing updated firmware versions, or offering an update module.